YELLOW FEVER 237 



Carrol and Reed that the female Stegomyia fasciata (also called 

 Steg. calopus) is the means of its propagation. Carrol believes that 

 the undiscovered parasite of yellow fever is of the animal kingdom, 

 for the following reasons: i. It is absolutely necessary for its con- 

 tinued existence that it undergoes alternate generation in man and in 

 the Stegomyia mosquito. This is peculiar to the sporozoa. 2. The 

 fact that two weeks must elapse before the mosquito is capable of 

 infecting man is evidence that a cycle of development of the unknown 

 parasite is taking place in the mosquito. 3. The limitation of the 

 cycle of development of the parasites to a single genus of the mos- 

 quito and to a single vertebrate (man) conforms to a natural zoologic 

 law, and this does not conform to our knowledge of the life history of 

 bacteria. 4. The effects of climate and temperature on the life 

 history of the Stegomyia, and on the rate of development of the 

 parasites in the bodies of the mosquitoes are exactly the same as the 

 effects of the same conditions on the anopheles mosquito and the 

 malarial parasite. Without the Stegomyia there can be no yellow 

 fever. Infection requires the fulfilling of the following conditions: 

 i. By the bite of the mosquito providing the insect has fed on 

 the blood of a yellow fever patient within the first three days of 

 the fever. 2. The disease is -not transferred immediately, but a 

 definite incubative period of more than eleven days must elapse 

 before the mosquito can transfer the disease. After twelve days 

 the mosquito has been found to be infected for at least fifty-seven 

 days. 3. Yellow fever cannot be carried by fomites. 4. Yellow 

 fever may be produced in a healthy man by the subcutaneous 

 injection of blood from a yellow fever case (parasites in the blood). 



5. The serum of a yellow fever patient filtered through a very 

 fine Berkefeld or porcelain filter is still capable of setting up the dis- 

 ease if injected, proving that the infection agent is submicroscopic. 



6. An attack of yellow fever produced by the bite of a mosquito 

 confers immunity against subsequent infection. 7. The period 

 of infection is usually three days but may be from two to six days. 

 8. A house or ship may be said to be infected with yellow fever 



